1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device and a method of processing a substrate, the methods including a process of forming a thin film on a substrate, and a substrate processing apparatus suitable for the process.
2. Description of the Related Art
A flash memory includes an electron accumulation region (floating gate) surrounded by an insulating film and operates in a manner that information is written in the flash memory by electron exchange through a thin tunnel oxide film and the stored information is retained for a long time by holding electrons using the insulating capacity of the thin tunnel oxide layer. Such a flash memory is required to retain the stored information for a long time, for example, even 10 years, without requiring any external operation, and thus stricter requirements are imposed on an insulating film surrounding a charge accumulation region which is called a floating gate. A stacked structure of oxide film (SiO2)/nitride film (Si3N4)/oxide film (SiO2), which is generally called “ONO” structure, is used as an interlayer insulating film between a floating gate and a control gate configured to control the operation of a memory cell, and it is expected that the ONO structure has low leak current characteristics.
In the related art, a SiO2 insulating film of an ONO stacked structure is formed by, for example, a chemical vapor deposition (CVD) method using SiH2Cl2 gas and N2O gas at a high temperature of about 800° C. (for example, refer to Patent Document 1). However, as devices become finer and highly integrated, there arise problems such as deterioration of step coverage characteristics and dependence of a film thickness on pattern density difference, and thus it is necessary to solve such problems.
In addition, a film-forming method for a flash memory is required to have improved productivity and change into a CVD method using SiH2Cl2 gas and N2O gas for high productivity.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2001-85333
When a SiO2 insulating film is formed, more amounts of atoms other than silicon (Si) and oxygen (O) included in a source used to form the SiO2 insulating film may remain in the SiO2 insulating film as impurities if the film-forming temperature is reduced. For this reason, if a SiO2 insulating film is formed by using an organic source gas, atoms such as carbon (C), hydrogen (H), and nitrogen (N) included in molecules of the organic source gas may remain in the SiO2 insulating film as impurities. In addition, although an inorganic source gas is used, atoms such as hydrogen (H) and chlorine (Cl) included in the inorganic source gas may remain in the film as impurities. Since such impurities lower the quality of an insulting film significantly, it is necessary to improve the quality of the insulating film, for example, by increasing the formation temperature of the insulating film. However, if the formation temperature is increased, since the thickness uniformity of the insulating film is significantly decreased, it is difficult to apply this temperature increasing method to production.